Process of treating rubber latex



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This invention relates to processes of so muchof it is required as when soap is treating latex and it comprises a process used. About one half rcent of saponin, wherein rubber latex, advantageously conbased on the weight latex, issuflicient. 1381111115811 added foam stabilizm agent, is Gelatin, lue, and numerous other subaerate and agitated to form a sti foam and stances, a having the roperty of assisting as the resulting foam treated to sohdify the in, and stabilizing the em formation, may rubber therein. be used. Rubber latex itself will form a Numerous processes have been proposed foam however, and the additional foam stafor the roduction of porous or cellular rubbilizing a ts can be omitted if desired. I

her. It as been suggested to coagulate rubfind that tter results are obtained when 0 her m such a way that voids or cells are left the foam stabilizing agent is resent. in the rubbe mass. It is possible, for in- In a ractical embodlment o my proccss,I stance to coa gulate rubber latex 'with acetic maintain a bod of stabilii ed latex, the maacid in such a fashion that the rubbely ma s terial purchasa 1c in the open market, in a V Id vessel having a perforated plate disposed of various sizes. It has also been proposed lightl above th b tt Th latexhom to prepare a porous rubber by nnlhng vqlataining an added foam stabilizing agent, say tile ea ts into rubber and thereafter heatm one percent of ordinary soa rests on the the rubber mass to volatilize the salts an rf t d l t d i h ld th b i 0 thus form voids or spaces. introduced eneath the plate. The intro- 7 These prior'processes have num ro duced air rises through the layer of latex advantages. In the coagulation process, 1t d forms f Th -f i it t d is d fficult to et porous. r ber f llhl lm. with an agitator of convenient construction cpmposltlon t ughout. Besides this, th to subdivide the bubblesformed and agita- S126 Of the VOIdB and their dIStllbulllOll tion is kept up until the, foam is dense, At 15 throughout the mass varies. Only comparathe com letion of the process, the foam. is tively large size voids or cells can be formed. it-, ti d h lds it h Th b bbles Where a volatile salt added to rubber 5 in the foam, at the end of the foam forming incorporated therem,1t 1s d1fliou1t to get un process ill b f nd t h v a b t tially so form incorporation and here again, there is if i d ill b if l di so no certainty that one batch will have the t ib t d' th h t th f Th bubbl s same ph s1c al characteristics asv another. ill b f i'i t i Ind ed, ith a well Uniformlt 1S dlfiiclllt t0 Obtam- -beaten foam, they can hardly be detected I have ound that ordinary rubber latex ith t if i l Th foa has containing as usual about th1rty percentof a creamy appearance, h like hi ped as rubber, can be converted into a foam by passcream, I ing air into the latex and agitating and that Th m md foam i then treated to the foam so formed. can be dried to form. fix o solidi the rubber in it. The foam sheets for instance of rubber containing can b sprea out-in heets and left to dry 40 minute voids or cells. It is advantageous i hi h case, h t f porous r bb are to add a foam agent t0 the atex obtained havin minute pores evenl dig. before passing in the am Such foam stat ib t d th t, Th h t b V so g llgents Well known- 'P 9 pre ared has the feel of chamois leather instance 18 exeellent. About 0118 percent of and ig exceedingly porous It can absorb ordinary soap is dissolved in the latex and a large amount of water and may be put to 06 thereafter air is introduced with agitation. numerous uses. It ma be used in storage" The process is much like beating an egg or batteries, as a filter m up, in surgical belts whi ping cream and the resultm foam is and the like.

sti and stable. Sa nin or soap ark is an When the foam is dried, which, advanexcellent foam stab agentto use. Not tageously, is carried out at room tempera- I ture or slightl above, some liquid may separate. slightly. This indicates that agitation of the foam has not been carried'far eriou h or that an insuflicient amount of air has een introduced. In such case, I the separated liquid is drawn off and the drying continued.

With a well beaten foam, beaten to such an extent that it becomes stifl" and tenacious, a condition readily reco nized, there occurs but little separation of liquid on drying. I attribute this to the fact that the rubber in the latex coagulates to some degree durin the agitation and in the partiall coagulate condition the rubber tends to sti en the foam and make it tenacious. During the beating up of the foam, the first formed bubbles, which are of comparatively large size, are subdivided so that eventually there results a foam having bubbles of minute size.

As stated, if agitation is not carried far enough, when the foam is spread out and allowed to dry, there may be some slight separation of liquid latex. In some relations this is advantageous, especially in coating fabrics, a use to which the latex foam may be put as hereinafter mentioned. The advantage in utilizing a foam having the property of breaking down slightly is that such a cam wets the fabric coated so that a strong rubber bond between the fabric and the rubber coating is secured.

When-the foam is to be dried to form sheets of porous rubber, it is more advantageous to carry out the agitation to such an extent that virtually no liquid latex separates on drying. The extent to which such agitation must be carried is readily determined by simple experiment. The characteristic of such a foam is that it is stifler and more tenacious than one in which agitation has not been continued to a degree suflicient to form such a foam.

Instead of using the ordinary latex of commerce, a so-called concentrated latex can be used. And a latex in which some partial coagulation has occurred, whereby-the latex is slightly thickened, is also suitable.

vulcanization, if desired, is best carried out on the dried foam, whether it be in the form of sheets or as a coating. The vulcanization is no part of the present invention. It entails no difficulties and processes are already known by which sheets of rubber, or coated rubber fabrics can be vulcanized.

Notonly do I regard the process herein described as new but I also regard the latex foam formed as a new composition of matter- The foam,-while it is an intermediate substance, may be transported and used in many relations. It, of course, may be dried or coagulated in the ;orm of sheets. It may be mixed with filing materials prior to drying or coagulation, for instance, in-

corporation in the latex prior to conversion That is, the foam may break down into a foam by processes well known. It

may be used as a coating material. It may be sfpread on a backing of canvas or the like to orm a coated material.

By the term latex in the appended claims, I mean of course to broadly include dispersions of rubber in an aqueous medium.

In the appended claims by the term dense foam, I mean to distinguish from a froth or foamy material. My foams are of such nature that they may be spread out to dry with but little or no breakdown of the cellular structure of the foam. The dried product is micro-porous. Froths or light foam which lose air are rapidly return to a liquid state when allowed to stand are not suitable for forming porous sheets of rubber or rubber coatings on fabrics. My foam is of such consistency that, during drying, substantially all of the water therein leaves the foam by evaporation and not as a 1i uid. That is, the foam actually dries out to orm a dry micro-porous rubber product. Such foams are stifi' in t e sensethat a small container thereof may be inverted without loss of contents but such foams-are of course spreadable.

In my copen'ding application, Ser. No. 406,978, filed Nov. 13, 1929, which is-a continuation in part of this application, I more specifically describe and claim rubberizing fabrics with latex foam.

Having thus described my invention, what I claim is,

1. In a process of preparing a useful ma-- terial from latex, the step which comprises introducingair into rubber latex containing a foam stabilizing agent and agitating the foam formed to form a stiif, dense foam, said foam being of such character that a layer thereof, upon drying, yields a porous rubber product.

2. The process which comprises forming a foam from rubber latex containing a foam stabilizing agent, said foam being of such character that a layer thereof, upon drying, yields a porous rubber product and thereafter solidifying the rubber in said foam.

3. The process which comprises forming a foam from rubber latex containing a foam stabilizing agent, said foam being of such character that a layer thereof, upon dr ing, yields a porous rubber product and t ereafter drying said foam.

4. The process which comprises passing air into a body of latex containing a foam stabilizing agent, agitating the aerated latex to form a dense foam and thereafter solidifying the rubber in said foam.

5. The process which comprises passing .air into a body of latex containing a foam stabilizing agent, agitating the aerated latex to form a dense foam and thereafter drying the foam.

m rial from atex, the step 13 a la er thereof, upon 6. Inaprocessofprepannfi' ausefulmaterial from later, the step w ch comprises agitating a bod of latex containing an a ded foam stab of a suitable gas to form a stifi, dense foam,

said foam being of such character that a yi yields 8 P r product rub FREDEBICKIL UNTIEDT.

agent in the presence yields a porous 

